From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 529E8CDB482 for ; Thu, 19 Oct 2023 12:14:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345496AbjJSMOk (ORCPT ); Thu, 19 Oct 2023 08:14:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46474 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233183AbjJSMOh (ORCPT ); Thu, 19 Oct 2023 08:14:37 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BDC00121 for ; Thu, 19 Oct 2023 05:14:35 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1697717674; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=58U0eUXdd4M6jZI9lKg9MYDjXA9pyTqDZLUuXlBoJw0=; b=GZoPHMjR5E4rPkZ3s/bu/sVO2VPM+SyrhdhfK0s3l70+lEDoLRAszLbTIexbIyQzyfxn4R UoI0u3s2BaXC4F6j+blqzge499LIKXwPVIhxRH2XpbXKcNerLXbsysySosH5Y9ch0Lw8j+ WQfEKTIAER9hZI37UANwWoRlLlQV8JGj9cadkke8/Y8T1kBPDMqxdFHfiEnT8UB69hyusw l6mkfJI/ATDq+UyR0o/gOI6ED6nyZ9ij5Lem95Ca2iKJEn9JmDUzTnblKFBJSpu8LYx4KJ SSHcMHkA9J9JA5cgYVzTo/ys5T2pWcL8PeR662dn1H54iTMMFwzlcHViy/3mkg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1697717674; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=58U0eUXdd4M6jZI9lKg9MYDjXA9pyTqDZLUuXlBoJw0=; b=7yExDj+tM7UeVAQmasjeeBaRpV86CZ5qFF0wxbSmY+APAlANXqp52rLMcOGCITsf3ONk3+ I5kNWwGwwfcUY+BA== To: Tetsuo Handa , paulmck@kernel.org Cc: John Stultz , Stephen Boyd , LKML , Sebastian Andrzej Siewior , x86@kernel.org, joel@joelfernandes.org Subject: Re: [PATCH] clocksource: disable irq when holding watchdog_lock. In-Reply-To: <5ef329fe-1f3b-4d81-9625-9738620f051e@I-love.SAKURA.ne.jp> References: <80ff5036-8449-44a6-ba2f-0130d3be6b57@I-love.SAKURA.ne.jp> <878r826xys.ffs@tglx> <90361195-4309-4a02-bd3f-8ee606e6d35b@I-love.SAKURA.ne.jp> <5ef329fe-1f3b-4d81-9625-9738620f051e@I-love.SAKURA.ne.jp> Date: Thu, 19 Oct 2023 14:14:34 +0200 Message-ID: <87r0lq3j2t.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 19 2023 at 18:30, Tetsuo Handa wrote: > On 2023/10/17 23:10, Paul E. McKenney wrote: >>> But I'm hitting something different (but might be timer/scheduler related) problem. >>> What config option would cause taking more than 2 minutes to bring up only 8 CPUs? >>> (This environment is Oracle VM VirtualBox on Windows 11 host.) >>> >> The timing is about the same in both cases. Does this happen in kernels >> built with CONFIG_PROVE_LOCKING=n? > > Disabling all options in "Lock Debugging (spinlocks, mutexes, etc...)" does not help. > >> >> Either way, what mainline or -stable version is this? > > The kernel is latest commit of upstream linux.git tree. > I'm seeing this slowdown (almost hung-up) problem for many releases, > but nobody else seems to be reporting this problem. Maybe because of this: >>> (This environment is Oracle VM VirtualBox on Windows 11 host.) > The only reliable workaround is to specify "nosmp" kernel command line option. Which makes the kernel keep TSC as clocksource because there is no synchronization problem between CPU0 and CPU0 :) What is the fallback clocksource when the TSC is discarded on SMP? >From the dmesg snippets I assume it is the ACPI PMTIMER, which is I/O port based and presumably takes a VMEXIT on every read and depending on the emulation this might be slooooow. So you could boot with "nosmp clocksource=acpi_pm" on the command line and compare that against a "nosmp" boot. If my assumption is right, then on UP the ACPI PM variant won't see the massive slowdown SMP observes, but there should be still an observable difference. Thanks, tglx